EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78716
24 EW NEWS & OPINION March 2012 Complicated cataract cases Cataract surgery in the setting of prior pars plana vitrectomy: Surgical pearls by Arup Chakrabarti, M.S. posterior subcapsular cataracts. Older adults usually experience progressive nu- clear sclerosis. As the indications for pars plana vitrectomy expand and the number of procedures performed increases, the vol- ume of post-vitrectomy cataracts will in- crease in lock step. Cataract surgery in the post-vitrec- tomy eye is usually straightforward, espe- cially if the anterior cortical gel and vitreous face were spared. However, it can also be very challenging, especially if more than one vitrectomy was performed or silicone oil was injected into the eye. Unique fea- tures of post-vitrectomy eyes may include conjunctival scarring, small pupils, in- creased nuclear density, zonular laxity, trampolining of the iris-lens diaphragm, and the presence of posterior capsule plaques. Many of these problems are fur- ther aggravated if a scleral buckle is also present. C The visual potential of eyes that have undergone a vitrectomy is often reduced and patients' expectations for visual im- provement need to be managed appropri- ately. Epiretinal membranes and cystoid macular edema are especially prevalent in this population. In his article, Dr. Chakrabarti discusses pre-op considerations, IOL selec- tion, patient counseling, intraoperative con- siderations for each step of cataract surgery, post-op management, and post-op complications. Although experience comes with practice, those who are early in their careers and those who do not encounter post-vitrectomy eyes frequently will find many useful pearls in this article. Kevin Miller, M.D., Complicated cataract cases editor Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) Or view the video of Dr. Chakrabarti's procedure at www.eyeworld.org/replay.php. Figure 1. Conjunctival scarring in a vitrectomized eye Figure 2. Emulsified silicone oil in the anterior chamber Source (all): Arup Chakrabarti, M.S. ataract development is a com- mon complication of pars plana vitrectomy. Children and young adults usually develop Introduction Cataract development is one of the most common complications after vitrectomy; it develops in 12.5-80% of eyes.1,2 The risk factors for the development and progression of cataract are older age, degree of pre- op nuclear sclerosis, intraoperative lens touch, diabetic retinopathy, and silicone oil injection.3,4 The indica- tions for pars plana vitrectomy are fast expanding, and the number of patients undergoing this procedure is increasing because of the im- proved surgical results. Therefore, there is a significant increase in the volume of vitrectomized patients, who in their vitrectomized state pose a challenge to the cataract sur- geon. Risks in vitrectomized eyes The vitrectomized eyes are at a higher risk of developing intraopera- tive and post-op complications due to the following factors: 1.The eyes harbor sequelae of previ- ous surgery and inflammation. 2.They have associated comorbid conditions. 3.Nuclear brunesence (denser cataracts) is common. 4.They lack the support of vitreous gel. The following factors need to be taken care of while dealing with post-vitrectomy cataracts: 1.Conjunctival scarring (Figure 1) 2.Compromised corneal endothe- lium (Figure 2) 3.Poor pupillary dilatation 4.Zonular weakness and pre-existing posterior capsular rent 5.Low scleral rigidity 6.Cystoid macular edema 7.Diabetic retinopathy 8.Increased lens-iris diaphragm retropulsion Pre-op considerations A thorough pre-op evaluation taking into account the patient's compro- mised ocular health, structural changes resulting from the trauma of the earlier surgical procedure, and the poor visual potential is necessary in formulating a definite surgical plan. Pre-op examination should make note of the following impor- tant findings: The presence of con- junctival and episcleral scarring, endothelial cell count, deep anterior chamber and presence of emulsified silicone oil bubbles in it, presence of iridophacodonesis indicating a com- promised zonule, pupillary status, and detailed examination of the retinal status, especially to assess the integrity of the macula, and the presence of open breaks. In eyes with advanced cataract, assessment is made using a B-scan. B-scan in the presence of silicone oil, however, gives very few relevant details and has limited utility. Pre-op considerations should also include IOL choice. Both the hydrophobic and hydrophilic acrylic IOLs have been associated with con- sistently satisfactory outcomes and have been well tolerated by the eye. A rigid PMMA IOL may also be con- sidered. A silicone IOL should be avoided in an eye that has under- gone prior vitrectomy. Also, one- piece plate haptic-design lenses and lenses with small and ovoid optics should be avoided. Silicone oil can interact with the posterior surface of the IOL in patients with a posterior capsular rent, impairing visual acu- ity as well as fundus visualization both intra- and post-operatively. Sili- cone oil adhesion to the IOL surface is maximized with the silicone IOL. However, it can also occur with hy- drophobic acrylic, PMMA, and hy- drophilic acrylic lenses in decreasing order. A surface modified heparin- coated IOL can reduce the post-op reaction. A lens with a 360-degree square edge design with a large optic diameter (6-6.5 mm), which gives a greater viewing area for fundus visu- alization, is preferred. A plano con- vex configuration of the implanted IOL with the plano surface facing posteriorly ensures minimal refrac- tive surprises. Finally, pre-op patient counsel- ing should be included in pre-op considerations. It is necessary to give the patient a realistic idea of his visual potential as well as to make him aware of the expected and un- expected intraoperative events that can complicate his surgery. The benefit of the surgical inter- vention to the patient may provide an improved color perception, better peripheral vision, or only a better view of the fundus for the ophthal- mologist. The patient may be both- ered by diplopia, metamorphopsia, central scotoma, or anisometropia. Surgical strategy for phacoemulsification in vitrectomized eyes Long-acting cycloplegic and NSAIDs should be started at least 1 week prior to the surgery. This may help continued on page 26